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<head>
    <meta charset="UTF-8">
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    <title>Document</title>
</head>
<body>
    <script>
        var count = 123;
        function fn() {
            console.log(count);
            
        }
        function fun(num) {
            console.log(count);
            function foo () {
                count = 234;
                console.log(count);
                fn()
            }
            console.log(num);
            foo()
        }
        fun(456)
    </script>
</body>
</html>